Flat roof

I am about to close on a house with a flat roof (10 year old tar and gravel). Although there was no leaking, my inspector showed me 3 areas where the water was pooling from a storm the night before (Houston). I was planning on putting an white acrylic coat on called Evercoat 500 from everestscoatings anyway just to feel more comfortable and lower my utilities. I was told I could lay it over/on the rocks or take the rocks off.

Does anyone have an opinion on this? I suspect I’ll need to do something about the pooling areas. Is there a simple fix I should attempt before I coat it? What is the the basic life span for tar a gravel roof? Should I be looking for a totally new roof and if so what do you recommend?

Your thoughts and opinions would be greatly appreciated. I could use them as I negotiate the closing.

remove roof install TPO or have aaron spray some Polyurea …

Coatings … cannot be installed over any loose materials

by the time you get done power washing your roof and cleaning it enough might as well install a new system …

asphaltic membranes are not covered in the warranty by areas of ponding water.

Drains another option if its possible to connect them .


Just a tought … I am not a flat roof expert


Do not let an home inspector get you to upset. Most do not have a clue what they are talking about. And this one telling you there should be no water on a flat roof after a rain, does not know what he is talking about.

I had one tell the mortgage company that a slate roof needed to be replaced. They would not listen to me. I tore off a slate roof that had 60 to 70 years left. I replaced it with a 25 year roof. Just another home inspeptor who had no clue.

You will have water laying on flat roof after a rain. You will have water laying on flat roof after a rain. You will have water laying on flat roof after a rain. You will have water laying on flat roof after a rain.

If the water is there after 72 hours on a smooth roof. You may have a problem. The gravel will hold water even longer.

Without looking at the roof I could not tell you how long the roof will last. I am from Pa. That roof could last another 20 years here. If you try to do anything with your skill level, the lifespan could be 3 weeks.

i fix leaks sometimes by sweepin back rock and usin a water base cool seal over the rock.

so it will work, but it will be alot of work.

may want to tear off and put on white roof


I think you’d better read the mfg literature on the Everest coatings. If it is elastomeric Acrylic, then you absolutely should not use it in ponding water areas. It will eventually dissolve under standing water.

If it is a urethane based coating, then it would stand up, most likely, to the water, but still no good on a ballasted BUR. If you remove the gravel you are most likely going to be remveing your roof anchor. The gravel on a tar and gravel roof is primarily used as a ballast.

If it aint broke, dont fix it. If youre well-insulated on this section, it may or may not do any good.

[quote=“AaronB.”]I think you’d better read the mfg literature on the Everest coatings. If it is elastomeric Acrylic, then you absolutely should not use it in ponding water areas. It will eventually dissolve under standing water.

If it is a urethane based coating, then it would stand up, most likely, to the water, but still no good on a ballasted BUR. If you remove the gravel you are most likely going to be remveing your roof anchor. The gravel on a tar and gravel roof is primarily used as a ballast.

If it aint broke, dont fix it. If youre well-insulated on this section, it may or may not do any good.[/quote]

Actually Aaron, the gravel on a BUR was primarily used for fire-rating, but nowadays it is a good way to protect the membrane from deterioration due to prolonged exposure to ultraviolet solar radiation.

The story goes, or so I’ve been told, that rock was initially installed on roofs to protect them from burning embers. Remember, people haven’t always had furnaces, and they used to use their fireplaces and chimneys alot more. In addition, buildings along rivers like the Mississippi had to combat the embers discharged from the smoke stacks of river boats and such. So, the rock was applied to built-up roofs to help prevent them from catching fire. As time passed, people continued to put gravel on built-up roofs not only for fire-rating, but also because it was found to protect the roof membrane from sunlight.

In addition, if gravel was used as ballast for a BUR, why would there be slick-coated or smooth BURs? In a lot of cases, May Dept Stores being one example, building owners have gone away from stone aggregate surfaced built-up roofs, and have gone with built-up roofs that are aluminum coated or have an emulsion and aluminum coating applied to the finished plies.

What we both know is the mechanical fasteners installed in the roof board insulation, base sheet, etc., or the full moppings of hot asphalt are what attach the BUR to the substrate. I’m sure you are familiar with FM I-60, I-90 and I-120 ratings, and that to achieve the higher ratings you typically will be required to install more fasteners. Also, as a rule, more fasteners are generally required along roof perimeters and corners.


Where in Houston do you live? I’m on the west side over near West Oaks Mall.

Anyway, if your built-up roof is only 10 years old, it should still be in good condition. However, the truth be known, it also depends on who installed the roof to begin with. As for the ponded water, most roofing material manufacturer’s require water to drain or evaporate off the roof surface in 48 - 72 hours. So, depending on the size and depth of the water, it may not be a big deal. What you really need to do is post some photographs for us to look at, and then we’ll be able to better advise you.

Aaron also told you right, in that you want to stay away from acrylic coatings, and use urethane coatings. However, you do not want to use a coating over stone aggregate on your built-up roof.

Once again, show us some photos.

I agree with Aaron. If it aint broke don’t fix it. I would just make the buyer aware of the exact situation. 10yr old low-slope asphalt roof that ponds water but doesn’t leak. Should last until it leaks, then it’s time to start patching. They can “spud” or scrape rocks away and patch. Torch down maybe? That is if the leak is pinpointed. If this is a small enough roof then I would have it replaced instead of putting on band-aids and crossing our fingers. Plus that looks very ugly if the roof is visible at all.

Sam Bailey
Leak Chasers Roofing
206 551 6759

“If it aint broke don’t fix it.”

I don’t know if I would go that far. There is such a thing as roof maintenance, and if performed properly, should help extend the service-life of a roof. Now, that doesn’t mean that he should jack with his roof, because I haven’t seen any photos of the roof yet.


How would you do maintence on a gravel roof?

cerberus, you have crossed the line with your B.S. stories.

The ballast on BUR is just that…ballatst if the system is not mopped direct to deck, or to a mechanically fastened board stock.

Now granted, you can nowadays applyt a perfectly good BUR over a mechanically fastened board, sheet, etc. BUT if you ever tear off flat roofing, when you dont want to nor see the need to penetrate, the gravel aggregate has performed this duty exceptionally. For at least a hundred years, in fact.

Now, for way back in them olden days, it may very well have hed some ember-fighting abilities, and it does a rather shallow job of reflecting UV rays. (around 30% new and 20% aged reflectance if I recall correctly.

As far as UV protection, sure, it could help, but if we examine the larger scheme, would it be worth the exrtra cost to cover a perfectly coatable BUR in gravel? UV reflective coatings have been out for about 50 years.

Although your assessment has some actual conditionsd related to it, your history and reasoning are off base in this matter.

Please do not remove your gravel without first finding out if your roofing system is ballasted, solidly mopped, or mechanically fastened to the deck.

This pic is us installing a base and 3 with floodcoat of 60 lbs per square, and 500 pounds per square of ballast. This was for The Cook County Forest Preserve District. The gravel is primarily a ballast over the concrete deck.


Heres another building on the same project. Same specs.


You know Aaron, I was going to write a scathing reply to your post, but I decided to be the bigger man.

BTW, you do understand what it is I do for a living, right? I am a roofing consultant, which means I design roof systems, inspect roofing contractor’s work, develop punch-lists, survey existing roofs, perform testing (nuclear back-scatter, infrared, wind uplift, fastener pull-outs, etc), deal with property owners (management companies, governments, building owners, school districts, etc.), I handle bid documents, requests for payment, bid bonds, warranties, court testimony, etc.

Anyway, I wouldn’t recommend you install a loose-laid built-up roof with stone aggregate used as ballast. All the manufacturer’s I’m aware of, Johns Manville, GAF, Firestone, US Intec, Tamko, Performance, etc., want their system screwed, mopped, nailed or adhered to the roof substrate. So tell me, who are you installing loose-laid BURs for, and who is doing the design work? Do you have any manufacturer’s spec numbers? And who is warrantying these loose-laid roofs?

Back to the stone aggregate. Does the stone applied to a BUR help the roof resist wind uplift? Yes, absolutely, but that isn’t its main purpose. The stone or slag (for us old-timers) is applied in a flood-coat of asphalt that covers and protects the roof from fire and sunlight. Have you ever seen unprotected roofing felts after 90+ days in the sun? You mentioned reflectivity, and yes coatings are more reflective with regard to heat-gain, but we aren’t talking about that. The stone and asphalt protect the plies from UV solar radiation which deteriorates both fiberglass and organic felts. So, the asphalt flood-coat and stone aggregate are applied over the felts to protect them from the sunlight, and yes opaque stone is used for its reflective qualities as opposed to covering a roof with lets say coal.

Just so you know, I’ve been dealing with built-up roofs for over 25 years. So I suggest if you don’t know what I’m talking about you should either take notes and learn something, or don’t say anything at all that makes you look foolish. You know, I respect your knowledge with regard to coatings, and QRFL’s knowledge about shingle roof ventilation, gweedo’s know-how on tile, and the others for what they do best. I have never told any of them they’re full of sh*t, and I request the same courtesy from you. If you can’t respect me and what I do and know, then don’t expect me to repect you. Do we have an understanding?

Built-up roof that is not ballasted:


Infrared scan of roof, wet insulation glows white:


Well i wont take credit for the little bit i know of ventilation … most of it i learned from gtp 1003 … He has taught me a lot by chat … that and some sales … just wanted to mention it …

As far as i know sometimes Aaron and Cerberus they loose me with their technical stuff … So they both sound they know what their doing :wink:


Lol i know what this is but it looks like those bunker bombing missions in iraq



cerberus, you can be as mad as you like, I am not attacking you.

GAF warranted my roofs in those examples. All the tech data I have refers to bottom sheet attachment (base) to whateever the substrate is. So…over concrete roof deck, you MUST mechanically fasten? I think not. Specs say not, but you say yes.

Yep, like in your picture, if you do not ballast, you must mechanically fasten. You hit that on the head.

If you have ever noticed a ballast spec, the aggregate is listed in pounds per square, not a uniform thickness or reflective value. This is because you need XXX pounds per square per roof height per weather zone. Different zones and building heights have different wind needs.

Dude, I have been tearing off 40 year old ballasted BURs for two decades now. They work all over and they do a good job. Yep, smooth surfaced BUR only lasts about ten years here. You had that right also.

Please explain why you wouldnt use a highly reflective coating for UV barrier rather than a HEAVY much less reflective stone aggregate? For foot traffic? Sure, but that is prettty costly for foot traffic issues.

Please also explain to me why there are graveled Modified bitumen specs.

even nn-b-4-g would not be trusted because you do not mop under stratavent, but over it after it is laid out. This is a ballasted roof. Tee ballast is for weight.

Cerb, heres one that had a hundred years of roofing on it.

Three roofs, not a nail or fastener in any of the layers…all ballasted.


Here’s another we re-roofed. THe original was 25 year old loose laid ballasted BUR.


Did you actually bother reading my posts?

I didn’t say you had to mechanically fasten to a concrete deck. I said the roof system needs to be either screwed, nailed, mopped, or adhered. I also agree with you that single-plies can be ballasted. I disagree with you that it is acceptable to install a loose-laid BUR weighted down with gravel. As for the weights, that is no different than saying you need 25 pounds of asphalt per square, it doesn’t mean you need the 25 pounds as ballast.

As for your stratavent, it has holes in it so asphalt moppings can adhere it to the substrate. If you look at your GAF Application and Specification Manual, I just pulled mine out, look at pages 194 - 197, and you will notice that all of GAF’s roofs require some sort of attachment method. Under the caption Bottom Sheet Attachment, they offer the following methods: Torch, Mop, Nail, Screws & Plates, Mop to Perlite, Fastener, and Spot Mop. No where does it say you can loose lay your roof and ballast it. Maybe you live in some area of the U.S. that manufacturer’s waive the requirements put on the rest of us, I don’t know, but I can tell you I’ve done consulting from NY, Chicago, Miami, Houston, D.C., and Hayward (California), and I’ve never seen a ballasted built-up roof. All the built-up roofs I’ve dealt with have been secured to the roof deck in some way, shape or form. Whether it be with Insta-Stik, tube-lock fasteners, asphalt, cap nails, base sheet fasteners, or whatever.

As for the smooth-surfaced BUR only lasting 10 years where you live, they could last longer if the owners properly maintained the roofs by having them periodically re-coated. Unfortunately, with most owners the roof is out of sight, and out of mind. They only think about their roofs once they begin to leak.

So anyway, tell me more about your “ballasted roofs.” Do you get a FM (Factory Mutual) rating against wind uplift? If so, what kind of rating do you get, because I can’t imagine it is more than FM I-60 if FM will even rate your roof.

And no, I’m not mad at you personally. I just don’t appreciate you calling my information “b.s. stories” out of your ignorance. And no, I’m not calling you stupid, ingnorance is a lack of understanding or knowledge. Believe me, I’ve come across old roofers that have questioned what I tell them, and they respond with the “I’ve been doing it this way for 40 years.” Unfortunately, I then have to tell them “well, you’ve been doing it wrong then for 40 years.” Point being, I enforce the material manufacturer’s specifications and requirements, and sometimes during design our requirements exceed the manufacturer’s. For example, on a mod. bit. roof the manufacturer may require a minimum 4-inch end lap, and I may specify a minimum 6-inch end lap. Well guess what, if you are doing work for me you will have to install 6-inch end laps (I actually prefer 9-inches) if you want the building owner to pay you for the work. If you base your bid on my specs, then I expect the work to comply with the specs.

As for you and your loose-laid BUR’s, remind me never to let you bid or work on any of my projects. That is especially true here in Houston, as you would loose your roof and the stone aggregate would become projectiles during tropical storms and hurricanes. BTW, I’ve done consulting work for Cook Co. on several Chicago Fire Stations, and none of those had ballasted BURs. At the same time, I suspect you may install additional gravel on BURs near the lake due to straight-line winds, but that would be something peculiar to your area and not the rest of the U.S.

Put it this way. Guys, how many of you have loose laid a base sheet, mopped your roofing plies to the base, and then weighted it down with a bunch or gravel? Anyone else here put on a roof like that other than Aaron? I mean, I’m always open to learning something new. I won’t ever specify a loose-laid, ballasted BUR, but I’d be interested to know that are people actually installing them.

You’re right QRFL, it does look like a bombing mission.

Here, try this one instead: